Yes-you can upgrade from Vista, but not from XP.
Go to the Start button (bottom left). When the menu comes up, Right click on Computer, and choose Properties.
At the top middle it will show you what version you are running, as well as providing a link to update.
Click that link, choose your upgrade, and pay Mr. Gates with your credit card.
Download your desired version of Windows 7, and it will install and upgrade everything automatically.
Takes about 2 hours.
What you said. I upgraded a Dell laptop from Vista to Win7 with no problems — the only difference was, I bought the software. Totally seamless.